The present invention relates to semiconductor manufacturing apparatus, in particular equipment that includes an ash chamber for ashing photoresist, when making semiconductor devices.
To make a semiconductor device, several layers of different types of material are deposited on a substrate, e.g., a silicon wafer. Some are metal layers that must be etched to create devices and interconnects that form the desired integrated circuits. A photolithography process is used to define the sections of the metal layers that must be removed. That process may include the following steps: depositing a layer of photoresist, masking portions of it, exposing the masked layer to light that has a selected wavelength, then developing the unexposed portions. This process leaves hardened photoresist over the sections of the metal layer that are not to be removed and exposes sections of the metal layer that are to be etched.
After those exposed portions are etched, the remaining photoresist must be removed. An ashing step is generally used to remove the photoresist. That step may require placing the wafer in an ash chamber, then exposing it to a plasma, which reacts with the photoresist (in effect, burns it up), removing it from the wafer surface.
To facilitate photoresist removal, the susceptor (upon which the wafer is mounted) may be heated. To ensure that this practice does not crack or break the quartz bell jar that is positioned within the ash chamber base (hereinafter xe2x80x9cash basexe2x80x9d), a coolant (e.g., water drawn from a municipal water supply) is typically circulated through the ash base. Circulating coolant through the ash base cools the ash base surfaces. Polymer residues (which comprise byproducts of the plasma generation process) may form on those cooled surfaces. Those residues can flake off the ash base walls and drop onto the wafer. This can generate surface particle defects that can ruin one or more of the semiconductor devices that are being formed on the wafer. In some cases, such particles can cause an interlayer dielectric (xe2x80x9cILDxe2x80x9d), which is deposited over the etched metal layer, to tear as it is being polished. Such ILD tear outs can damage multiple die that are positioned adjacent to the one upon which the particle is lodged. As the critical dimensions for integrated circuit devices continue to shrink, even very small particles can cause fatal defects.
Accordingly, there is a need for an improved semiconductor manufacturing apparatus that reduces the number of semiconductor device defects that result from the photoresist ashing process. There is a need for such an apparatus that reduces residue deposition on ash base surfaces, thereby decreasing surface defects. The present invention provides such an apparatus.